1. Field of the Invention
The present invention relates to a technique for forming a silicon-containing film. More specifically, the present invention relates to a sputtering target material for forming a silicon-containing film, a method for forming a high-quality silicon-containing film using the same, and a photomask having the high-quality silicon-containing film.
2. Description of the Related Art
Recent years, in the field of semiconductor processing technology, the technology for miniaturization of a wiring pattern to constitute a circuit and miniaturization of a contact hole pattern for inter-layer wiring to constitute a cell has been increasingly desired because of miniaturization of a circuit pattern due to higher integration of large-scale integrated circuits. To meet such a demand, the wavelength of an exposure light used for photolithography is shortened from an i-line (365 nm) to a KrF excimer laser (248 nm). An ArF excimer laser (193 nm) is used for leading-edge industrial processing.
In the normally-used photolithography, a photopattern is formed by passing a light generated by a light source through a photomask, irradiating it to a resist film, and performing a pattern exposure on the resist film formed to process a substrate to be processed. At this time, the photomask is used for forming the above-described minute patterns and is further used as an original drawing for processing patterns. Accordingly, the photomask is required to have extremely high accuracy. Thus, a film for constituting a blank (photomask blank) used for manufacturing a photomask is required to be a film having high processing accuracy and extremely low defects.
As a material for a light-shielding film which is one of composition elements of the photomask blank, a silicon-based material from which a film having high processing accuracy can be easily obtained has started drawing attention. The silicon-based material has been conventionally used as a material for forming a halftone phase shift film in manufacturing a halftone phase shift mask (see Japanese Patent Laid-Open No. 7-140635). An optical film formed from the silicon-based material containing nitrided or oxidized molybdenum has high controllability of light transmission characteristics. Further, high processing accuracy can be easily obtained.
As compared with a chromium-based material conventionally used for forming the light-shielding film, such a silicon-based material has excellent light-shielding characteristics for an exposure light of 200 nm or less and can be processed by fluorine dry etching which does not easily damage a resist pattern (see Japanese Patent Laid-Open No. 2007-241065).
Also, a silicon-based material film has an advantage in combining a technique for using an etching mask for processing with higher accuracy. In other words, the light-shielding film of the silicon-based material is processed using the chromium-based material as an etching mask, a processing error due to pattern dependency or side etching can be reduced as compared with when the light-shielding film of the chromium-based material is processed using the silicon-based material as an etching mask (see Japanese Patent Laid-Open No. 2007-241060). Thus, the light-shielding film of the silicon-based material has shown great promise as the next generation of the light-shielding film instead of the conventional light-shielding film of the chromium-based material.
For forming a silicon-based material film, a sputtering target of the silicon-based material is usually used. As the sputtering target of such a silicon-based material, a stand-alone silicon (see Japanese Patent Laid-Open No. 2004-301993), a silicon-based target containing a transition metal used for forming a silicon-based material film containing the transition metal are used. When a sputtering target of the stand-alone silicon is used for forming a film, particles are generated during a sputtering process because the electrical conductivity of the target material is low and therefore particle defects are easily formed on the obtained optical film.
Some techniques for suppressing the occurrence of particles from the sputtering target of the stand-alone silicon have been suggested. For example, Japanese Patent Laid-Open No. 2002-72443 suggests using a sputtering target of a single-crystal silicon. Japanese Patent Laid-Open No. 2003-322955 suggests using a sputtering target of which a specific resistance is lowered by adding donor impurities or acceptor impurities in a stand-alone silicon.